This invention relates generally to reconstructive oral surgery, and in particular to intermaxillary fixation devices used in the restoration and healing of maxillo-mandibular injuries, including the reduction and temporary fixation of teeth, teeth rows and jaw segments.
According to current practice, fractures of the lower jaw (mandible), the upper jaw (maxilla) and some wounds resulting from surgical intervention to correct abnormalities or to remove tumors, involve reduction and re-alignment of fracture segments followed by passive fixation of the lower and upper rows of teeth in the maximum intercuspation position. Oral and maxillo-facial surgeons, plastic surgeons, and otolaryngologists routinely wire the jaws together (intermaxillary fixation) to achieve reduction and maintain fixation during and following oral surgery.
The conventional procedure of wiring the jaws together is performed with a temporary splint in which two or more arch bars are attached to the patient's teeth by circumdental wires. The arch bars are cut to the appropriate lengths and are secured by the circumdental wires which are looped tightly around the teeth. The upper and lower jaws are drawn together by tightening inter-arch wires that are looped around hooks carried on each arch bar. The fracture segments are then manually guided into alignment as the inter-arch wire loops are tightened, until proper reduction and fixation have been established.
The attachment of an arch bar by a circumdental wire loop is detrimental to proper gingival health maintenance. The circumdental wires penetrate and blunt the papilla. Moreover, the circumdental wire loops intrude within the gingival sulcus where plaque accumulation begins, and thus hinder hygienic access. The resulting gingival penetration is the cause of inflammation as well as discomfort.
The handling and manipulation of circumdental wires during attachment of an arch bar places the surgeon at an intra-operative risk of skin penetration. Double gloving is used for increased protection, but decreases operator dexterity and does not guarantee safety. Obviously, the elimination of circumdental wires would substantially reduce the surgeon's risk to stick penetration.
Because of such risks and limitations, improvements in arch bar construction have been proposed in which acid-etch and direct cement bonding techniques are used for attaching the arch bars to teeth without utilizing circumdental wires. For example, Baurmash U.S. Pat. No. 4,904,188 discloses an arch bar that includes integrally formed ligature hooks and a layer of a metallic mesh material that is spot-welded onto the back surface of the arch bar for forming an adhesive bonding attachment to tooth enamel. The upper and lower arch bars carry upwardly turned and downwardly turned ligature hooks, respectively, for engaging intermaxillary ligature wires.
Krenkel U.S. Pat. No. 5,087,202 discloses a stabilizing splint that is bondable onto tooth enamel, the splint including a series of rings interconnected by bar segments, with adhesive being deposited into the bore of each ring. Intermaxillary fixation wires are engaged by upwardly and downwardly turned hooks.
Baehr U.S. Pat. No. 5,184,955 discloses a similar arrangement in which bonding rings are slidably mounted onto a metal arch wire. Upper and lower arch wires are connected together by interarch ligature wires.
U.S. Pat. No. 4,202,328 discloses an arch bar in the form of a flexible metal arch bar that is secured onto a row of teeth by a circumdental wire and retainer beads that project between adjacent teeth. Upper and lower arch bars carry oppositely turned hooks for engaging fixation wires.
U.S. Pat. No. 5,613,853 discloses another splint arrangement for stabilizing a row of teeth in which an arch bar is secured onto a tooth by a plastic tie cable that encircles the tooth and the arch bar. Interarch cable ties are also secured by upwardly and downwardly turned hooks carried on upper and lower arch bars, respectively.
U.S. Pat. No. 4,230,104 discloses yet another arch bar splint in which the arch bar is secured in place by circumdental wires that are looped around individual teeth. Intermaxillary fixation wires are secured by upwardly turned and downwardly turned tabs.
U.S. Pat. Nos. 4,068,379 and 4,165,561 to Miller et al disclose a metallic mesh or metallic foil base pad for use in combination with cement for bonding an orthodontic bracket onto tooth enamel.
U.S. Pat. No. 4,752,221 discloses an orthodontic bracket having a thin porous layer of sintered metal powder as a cement bonding base.
U.S. Pat. No. 5,110,290 discloses a metallic mesh screen forming a cement bonding layer for attaching an orthodontic bracket onto tooth enamel.
U.S. Pat. No. 5,256,062 discloses a non-metallic appliance formed from a transparent material such as crystalline alumina, together with a stainless steel metallic foil mesh bonding pad for adhesively bonding the transparent appliance onto tooth enamel.
U.S. Pat. No. 4,952,142 discloses light curable polymer bonding compounds in combination with a mesh bonding layer for attaching an orthodontic appliance onto tooth enamel.
U.S. Pat. No. 5,232,361 discloses an orthodontic bracket constructed of titanium and titanium-based alloys for supporting an orthodontic arch wire. The bracket includes a base portion that is adapted for adhesive bonding attachment to tooth enamel.
The Bauermash arch bar disclosed in U.S. Pat. No. 4,904,188 is typical of conventional arch bar designs in which oppositely turned hooks are attached to lower and upper arch bars for engaging intermaxillary fixation wires. According to that design, the tension forces applied through the intermaxillary fixation wires are primarily applied in only one direction, that is, in a direction opposite to the direction that the hooks are turned from the arch bar. A limitation on that arch bar design is that the interarch wires can easily slip off of the hooks and can also be cut by shearing engagement against the side edge portions of the hooks when the fixation wires are routed transversely with respect to the hooks, especially in a direction that is parallel to the longitudinal axis of the arch bar.
Moreover, the conventional upwardly and downwardly turned hook arrangements are intended for top-to-bottom tightening, and are not suitable for engaging transfracture wires in which substantial forces are applied between right and left jaw segments to obtain reduction. A further limitation on the use of conventional arch bars with integrally formed hooks is that the hooks are as thin as the arch bar itself and are flexible. Because of this flexibility, the hooks often bend and warp as the fixation wires are tightened. Consequently, when bending and warping occur, the hooks must be reshaped and it is sometimes necessary to retighten the ligature wires to maintain proper reduction and fixation.
A further limitation on the use of oppositely turned hooks for securing interarch ligature wires is the difficulty in engaging a gripping tool such as forceps to seize the hook and apply appropriate forces during application or debonding. Such hooks, of course, are not intended for debonding or engagement with conventional forceps, and so it is necessary for the surgeon to manually apply finger pressure against the arch bar during installation. This exposes the surgeon to risk of skin cut or puncture as a result of engagement against a sharp edge. Additionally, the arch bars become contaminated with the powder that is commonly applied to the surgeon's gloves, and such contamination can corrupt the cement bonding agent, resulting in reduced bond strength and premature bonding.
A further limitation on conventional arch bar arrangements that utilize direct adhesive bonding attachment of arch bars to tooth enamel is that such bonds are largely mechanical and initially require an acid-etch of the tooth enamel. The acid-etch step creates undercuts in the tooth enamel or the tooth dentin which increases the bonding surface area. After the hard surface of the tooth has been undercut, a liquid primer and a liquid adhesive are applied and cured, with the cured surface being mechanically interlocked with the undercut structure and bondable with adhesive. This acid-etch offset bonding arrangement provides a high strength, durable bond that is intended for long-term (typically 12 months or more) applications, as commonly employed in the attachment of orthodontic brackets. However, the debonding of such high strength bonding arrangements has resulted in enamel fracture and difficulty in complete removal of the brackets and adhesives from the teeth.
Moreover, the high strength acid-etch bond is achievable only by first obtaining a dry tooth surface. A dry tooth surface is difficult to obtain in practice, since the fracture zone is almost always bordered by moisture producing lacerations and soft tissue avulsions. An additional consideration in the use of conventional acid-etch adhesive bonding is that such cement compositions are formulated for long-term applications, for example the attachment of orthodontic brackets that typically remain on the teeth for twelve months or longer, and must provide long-lasting high bond strength. Most intermaxillary arch bars are designed to remain in place rarely longer than eight weeks, and in some instances the arch bars are used intra-operatively for only a few hours. Moreover, because of the high bond strength of acid-etched composite adhesive bonds, the tooth enamel can be fractured and removed along with the arch bars during debonding. Debonding of such high strength bonds requires the application of a powered handpiece, and some tooth enamel may be sacrificed as the cement residue is abraded from the tooth surface.